The stories of the Brush Development Company, Thermionic Products,
Racal-Thermionics and Racal-Recorders are told in "A Truvox
Product" - as will soon become clear!

Founded in 1944 by Alfred Colley and Edward Angold, both had
experience of piezo-electric devices and work on secret war-time
communications equipment. Their work drew them to that being
carried out by the American leaders in crystal and piezo-electric
technology, the Brush Development Company. Following an exploratory
visit to Brush in 1946, Angold became enamoured with America's new
electronic flash-guns while Colley saw a commercial opportunity in
Brush's magnetic recorders, developed by Semi Joseph Begun.

Thermionic Products' first product was Britain's first electronic
flash-gun, the 'Mega-Flash', but while they also developed patents
on cinematographic sound recording, their future lay in magnetic
recording. Having secured rights to an improved Brush
"Mail-a-Voice" disc recorder of 1946, they launched their "Recordon
TP503" in spring 1948 using a B&Y fan motor, built by their
subsidiary company. This was marketed as an office dictating
machine and operated very much like a gramophone, recording onto a
9" magnetic oxide coated paper disc which could be folded into
three and posted to another office, making it especially popular
with travelling salesmen.

The Recordon's success allowed the company to take up offices in
Jermyn Street, London. It was later produced at their new Hythe
works, as an improved TP504, along with a deluxe 'Diplomat' version
in 1953 which incorporated an intercom with the secretary and
telephone amplifier. The Recordon survived into the mid-1950s when
they took up assembly of the Swedish 'Agavox' recorder.

Thermionic Products duly secured the licence to build the Brush
BK.411 'Soundmirror'. This entered production in late-1948, albeit
being contract assembled by the Walter Instrument Company. This was
the first British-built domestic tape-recorder as the British
designed and built Wright & Weaire tape-deck did not enter
production until several months later. However, problems soon
became apparent with the quality of the oxide-coated paper tape,
made for them by the 'Butterfly' label business, as the oxide
shedded far too readily, and clogged the heads! While this was
being sorted out, Colley made a fortune producing the drinking-duck
novelty solar toys!

Promoting the new-fangled Soundmirror was problematic. While the 9"
disc Recordon had opened up the office dictation market, the
Soundmirror, with its 'Magic ribbon' tape, was aimed at longer
duration recording of lectures, meetings, concerts and in the home
to record memorable events, but it was a slow seller as Britain was
still suffering rationing. Never-the-less, the design was soon
licensed to European companies such as Carad, Tandberg and even
Studer.

The Soundmirror TP.411 was a single speed (7-1/2ips) machine and
one of the first to use a swinging arm pinch wheel operation. It
employed a cross-over belt drive with joy-stick control and
'pop-up' permanent magnet erase head. The 'full track' head used
only the central 2/3rds of the tape. Unlike today's 3-wing DIN
drive, the spools were driven by upturned flanges on the spool
turntable, later superseded by offset pin to engage DIN centre
spools. It sold at £69 in a superbly made walnut veneered cabinet
as a piece of domestic furniture, complete with large stick
microphone and internal speaker.

Production moved to Hythe, Hampshire in 1950 and soon faced its
first major British competitor, the well built Baird
'Soundmaster'. The table top Soundmirror was joined in 1951 by
the 'Portable' TP.414, in a wooden suitcase, finished in a
yellow/brown fabric, which had provision for extra spools of tape,
a large ACOS microphone and cables: it was surprisingly light! It
sold for £79. There was talk of a new 2-speed on-demand version,
possibly the new Brush BK.455, but those from Thermionic Products
were 1/2 track versions of the old Soundmirror in a slightly
modified cabinet with what appears to be optional factory-set 3-3/4
or 7-1/2ips - (can anyone confirm?). Production of the Soundmirror
continued to late 1954.

Multi-channel recorders

A new post-war Convention on International Civil Aviation brought
forth statutory demand from 1951 for the logging of all Air Traffic
Control to pilot communications. This required multi-track
machines, but while the Royal Aircraft Establishent and Simon
developed a indented recording (like a record) on 35mm film stock,
Brush and Thermionic Products developed multi-channel magnetic tape
voice loggers with the first all-British airfield recorder being
developed independently by Thermionic Products in London in 1949,
launched in spring 1950, after which Brush pulled out of further
magnetic tape development to concentrate on their core crystal
business, much to Begun's dismay.

The 14-channels were recorded on 0.7" wide paper-tape, initially
using interlaced 7-channel heads, in pairs of coupled decks
allowing continuous 24-hour recording, plus a replay deck. The
improved, slower running Series II (1-7/8ips) appeared in 1953 and
soon Thermionic Products were dominating the market: their decks
even recorded the fatal DH Comet crashes in Italy.

After George Colley died in 1956, the company became a subsidiary
of the expanding Pena Group in 1957, joining Cosmocord and
Peto-Scott. They were now pinning their hopes on a major contract
for recorders for London Heathrow airport, but it went to the
British Communications Corporation - a young company owned by
Daniel Dan Prenn of Truvox fame. The failure to win the contract
soon pushed Thermionic Products and Pena into financial
difficulties at which Prenn bought Thermionic Products in late-1958
and production of airfield voice-loggers continued at Hythe under a
new company, Thermionic Products (Electronics) Ltd leaving BCC to
concentrate on their core military and police radio
communications.

Audio Division

Colley was always keen to diversify and in 1952 the company offered
a range of (unknown) 'instruments for electro-acoustic
measurements' and 'Acousticel' microphones. In 1955 he gained
world-wide distribution rights to the new Kelly electrostatic
loudspeakers. Then from 1956 Thermionic Products added their highly
regarded TP100 audio amplifier and the 'Microlift' gramophone tone
arm lifter, later licensed to Decca.

Thermionic Products (Electronics) Ltd

Thermionic Products would remained world leaders in multi-track
recorders and with expertise gained through Epsylon and Vectron
engineers, expanded into instrumentation recorders and digital
technology.

In 1967, Daniel Dan Prenn transferred his 'Truvox' audio business
to his Thermionic Products operations; Truvox's audio and floor
cleaner production moved to Hythe but the Truvox Floorcare business
soon reverted to the Prenn family.

Thermionic Products' expertise in military contracts soon
transformed the quality of Truvox's domestic tape-recorders; indeed
the Truvox Series 100 was chosen as the basis for their first
portable instrumentation and seismic recorder, the T3000. This now
had four speed operation and advanced electronic pcb circuitry. It
was superseded by a modified Truvox Series 200 deck and alone
survived as the Racal-Thermionic T3000 when Thermionic Products and
Racal merged in 1969 following both Racal and Thermionic Products'
interest in the 'Clansman' military back-pack radio contract.

In addition to their multi-channel communication recorders,
Racal-Thermionic developed an incredibly versatile and truly
advanced portable instrumentation recorder, the Store 4, which
replaced the T3000. This offered optional speed ranges from
15/640ips (for seismic work) to 60ips in 4-, 7- and 14-channel
formats, the latter often used in industrial production control
processes. Highly regarded for its delicate and accurate tape
transport, it was the machine of choice for replaying fragile
aircraft "Black-box" tapes for crash analysis.

In 1971 Racal bought the Zonal (formerly llford-Zonal) magnetic
tape business but sold it in the 1980s; Zonal are still in
business. By 1977 the company had become Racal-Recorders and
further developed specialist communications and instrumentation
recorders, but these are beyond the scope of this audio web-site,
although are covered in the book.

Subsidiaries

Among the many companies who came under Daniel Dan Prenn's wing
were: Airmec, British Communications Corporation, Celestion, Modern
Aerials, Racal, Truvox, and Vectron. Their stories are also
recorded in "A Truvox Product".